Radiation attenuator for calibration

ABSTRACT

An attenuator for adjustment of photometers wherein interceptors are caused to periodically traverse a bundle of rays and beams at relatively high speed. Means are provided for constraining the interceptor means to move and be held in nonintercepting position when the traverse movement is discontinued.

VII-"\- uwuwvla Ur-l [72] Inventors Werner Seheler [56] References Cited UNITED STATES PATENTS Hubert Wenzel, Frankfurt/Main; Kurt mmnhuenobchlsrknhch'aud, 2,166,947 7/1939 Fayerweather 350/269 can, 2,494,440 1/1950 Haynes 350/274 X pp No 7703." 2,721,759 10/1955 Tashjian 296/97.3 2,986,063 5/1961 Etzenhouser 350/274 X PM a 426 293 2/1969 Snitzer 331/94 5 {45] Pmemed July's 197 [73] Assignee Hnrtrnnnn 8i Brenna Aktiengesellsehah Primary Examiner-Ronald L. Wibert Frankfurt am Main, Germany Assistant Examiner-T. Major Attorney-Franklin R. Jenkins [54] RADIATION A'I'I'ENUA'I'OR FOR CALIBRATION 9 Claims, 2 Drawing Figs.

[52] US. Cl 350/266, ABSTRACT; An attenuator for adjustment of photometerg 350/269, 350/273, 350/274, 350/275 wherein interceptors are caused to periodically traverse a bun- L511 Int. Cl 4 G021 1/30 dlg of rays and bgams at rclativcly high speed Mean; am pm. [50] Field of 350/266, vided for constraining the interceptor means to move and be 269, 273, 274, 275; 356/213, 214, 233, 217; held in nonintercepting position when the traverse movement 296/97 is discontinued.

mama] JUL em SHEET 1 BF 2 PATENTEDJUL sun 3.591.259

SHEET 2 [IF 2 RADIATION ATTENUATOR FOR CALIBRATION BACKGROUND OF THE INVENTION 1. Field of the Invention In a photometer wherein radiation attenuation is used to analyze material, a moving device for attenuating radiation during calibration and adjustment of the photometer.

2. Description of the Prior Art In the calibration and adjustment of photometers, say utilizing infrared radiation, for gas and liquid analysis, dimmers or attenuators in a beam path are used which are usually stopping diaphragms, colored glass filters or cuvettes filled with some light absorbing material. When the degree of attenuation is to be quite small the conventional means mentioned present much difficulty in their production. The standardization or adjustment by fixed diaphragms must be very precise lest the dimming not act uniformly over the cross section of the beam. The optical dimming means result in increasing cost and, because of reflection losses, not fundamentally suitable to effect very small gradations of dimming. Stationary dimming means also present problems owing to dust settling upon them so that there is a risk of error if no regular control tests and cleaning are provided for.

It has been proposed (as shown in German ausgelegeschrift 1,136,506) that a sector-shaped rotary attenuator be used. Such a device is generally satisfactory as far as dust is concerned but it does not provide fine gradations in attenuation.

Inasmuch as the dimming by the means of the prior art just described must be regressive the dimmer means is removed from the ray path, for example by withdrawing it or by tilting it, in such a way that under certain conditions the driving means also must be moved with the dimming means. In the case of a continuously operating photometer this is an inconvenient restriction since it is desirable to switch or throw the dimming agent into the ray path for the purpose of calibration without special manipulation each time it is done.

SUMMARY OF THE INVENTION The invention relates to an attenuation device for calibrating and adjusting photometers for the analysis of gases and liquids through which an analysis beam passes. Usually a reference beam is also present and an analysis is made by a comparison of attenuation of the two beams.

The invention provides a device whereby a blocking member may be periodically moved over the cross section of either or both of the beams in such a manner that the above mentioned disadvantages are eliminated.

Features of novelty are that the blocking member has an active plane that blocks out a fractional portion of the cross section of the beam to be dimmed, and during periodic movement moves out beyond the cross section of the beam, and provides for a device operable upon cessation of the periodic movement which brings the blocking member into a rest position outside the beam and holds the member in such position.

In the embodiment as shown the blocking member is so shaped that it embraces the beam when it has traversed same and is then without affect on the beam, this embracing position being the position of rest and is automatically attained when the means for moving the blocking member is rendered substantially inactive.

Another feature of novelty is that the periodic motion of the blocking member is powered by an electric motor, whose rotor is normally urged away from its stator and is made to approach the stator upon excitation. Upon substantially deenergizing the motor the rotor then moves away from the stator and this motion is exploited to effect movement of the blocking member beyond the beam to the rest position.

A further feature of novelty is that the blocking member is a wire loop whose wire diameter may be small to give a narrow shadow for very small amounts of blocking.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective showing one form of the invention, and

FIG. 2 is a perspective showing another form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the device according to FIG. I the attenuating element is a generally oval wire loop, which is held fast in a clamp 2 by the upper end portions 3 of the loop which are bent outwardly and downwardly.

The additional function of the clamp 2 is to couple the loop rigidly by means of the shaft 4, with the rotor 5 of a stationary incompletely shown electric motor above the clamp. A fixed position plate 6 to which the shaft is perpendicular is provided with a central opening 6' passing the shaft 4 and portions of the ends therethrough and having L-shaped slots 7 communicating with the opening 6. When the plane of the loop is perpendicular to the axis of fixed path ray bundle 8, the latter being surrounded by the loop, the rays are not affected and the ends of the loop are situated in the slots so that the loop is held against turning. Upon switching on the motor the rotor becomes drawn into the air gap of the stator, partially shown at 5', against the force of gravity as shown by the arrows 14 in FIG. I. The ends of the loop leave the slot and the wire loop can rotate free, being driven by the motor. Hence the oppositely lying sides of the loop are periodically passed back and forth over the cross section of the ray bundle, and the beam becomes attenuated or dimmed as a result. Very good results are obtained by the use of small synchronous motors, common in the instrument art, where their function depends on hysteresis action.

When the motor is cut out the rotor moves downwardly under the force of gravity, the ends of the wire loop touching the plate and dragging thereon and dissipating the kinetic energy of rotating until they fall into the slots in a locking manner. Hence the loop is stopped in a position where it does not affect the bundle of rays owing to the loop then lying in a plane to which the axis of the bundle is perpendicular.

It is obvious that upon the switching off of the motor that the accumulated energy of movement must be sufficient in each half turn for the loop ends to move to the slot.

The action can be obtained if instead of abruptly cutting off the motor, the power or speed is drastically reduced by a stepping switch. Upon reducing the power of the motor to a verysmall value the rotor also moves downwardly under the forceof gravity and the remaining moment carries the loop into the arrested position. In order to operate with certainty that the loop enter into the slot immediately and not only after repeated or several rotations, the slot is provided with an upstanding ridge 9 on the marginal portion of the slot and across therefrom in the direction of rotation. The ridge stops the rotary movement of the loop immediately; the loop ends cannot glide over the ridge and the loop is forced into arrested position. The device according to FIG. 2 has a square stirrupshaped loop dimmer element 10 of wire to form the loop and in general is similar to that of FIG. 1 but with a different means to bring the loop to nonoperative rest position. The same type of rotor and motor is used as in FIG. I, but in FIG. 2 the rotor shaft carries fast thereon a circular disc 11 provided with a downwardly open diametric wedge-shaped symmetrical slot 12 in the lower portion of the disc under the motor. The Element 10 is shown in upper position, due to the stator 5', and in an instantaneous rotary position. Beneath the disc 1 l is a mating similar disc 13 in axial alignment having the slot upwardly open but held in fixed position by means not shown. The shaft 4 isrotatable with respect to the disc '13. When the motor is deenergized, the rotor, disc 11 and stirrup 10 move downwardly under the force of gravity as shown by the arrows 14' in FIG. 2 and the disc 11 engages the disc 13 in jaw-clutch fashion. The disc 13 is so positioned that when the two discs mate, the plane of the wire stirrup is perpendicular to the axis of the ray bundle and the stirrup embraces the bundle and has no influence on the latter. The discs ll and 13 are preferably of metal and plastic respectively.

Another possibility for bringing the dimmer to rest position is to employ backlash of the rotor to close a contact switch for electromagnetically setting the dimmer in position by first drawing it into position and then holding it there.

Extremely small gradations of attenuation are produced by the invention and it succeeds in utilizing a rotary device in a simple manner by means ofan electrical switching in and out action. lf the motor speed is to be considered it is necessary that the period of duration of blocking out be small relative to the time constant of the electrical organization of the photometer, and so far as it concerns photometers with beam modulation, motor speed must be high with respect to frequency of modulation. Although the attenuation is intermittent, if the condition of a high speed relative to modulation frequency is maintained, the effect is a provision of a practically definite constant amount of attenuation.

We claim:

1. A device for attenuating a radiant energy beam in an analyzer depending on relative radiation absorption by fluids comprising: a rotary means for periodically blocking said beam including a wirelike loop for rotation within said beam about an axis transversely of said beam, the blocking portions of said loop being of substantially less area than the nonblocking portion enclosed by said loop, driving means for rotating said loop about said axis, fixed arresting means positioned about said axis for bringing said rotary means to rest in a nonblocking position relative to said beam, said driving means including means to move said rotating means out of engagement with said arresting means when said driving means are energized and to cause engagement with said arresting means when deenergized. Y

2. A device as claimed in claim l, wherein said drive means includes an electric motor having a stator and a rotor movable along the said axis and substantially rigidly connected to said rotary means, the rotor being axially aligned with the rotary means and being biased in one direction along the axis thereof when the stator is not excited and in the opposite direction when the stator becomes excited, said means for bringing the rotary means to rest including fixed receiving means and means fixed with respect to the rotor for entering the receiving means upon movement of the rotor in said one direction to bring the rotary means to a rotary position corresponding to said nonblocking position.

3. A device as claimed in claim 2, said rotor being biased by gravity in said one direction. I

4. A device as claimed in claim 1, the rotary means being a substantially mono-planar wire loop mounted for rotation about an axis to which the beam is generally perpendicular, the loop lying outside the beam when the loop is in nonblocking position and the axis lying substantially in the plane of the loop.

5. A device as claimed in claim 4, the loop being substantially symmetrical about said axis.

6. A device as claimed in claim 2 said receiving means being provided with a slot radial to the axis, and the means for bringing the rotary means to rest also include projections on the rotary means radial from the axis of the axis of the rotary means and developed in said one direction for entry into said receiv ing means the bias in said one direction urging at least one of the projections against the receiving means to slow the rotor sufficiently for the projections to enter the slot.

7. A device as claimed in claim 6, the receiving means being a plate to which said axis is perpendicular and having a radial slot, said rotary means including a substantially flat wire loop embracing the beam when in said nonblocking position, the

, loop having terminal portions forming said radial projections for entering the slot.

8. A device as claimed in claim 6, said receiving means being a round bushing containing a V-sha ed notch thereacross open toward the rotor to provide sai slot and a similar slot as a continuation thereof across the axis, and a similar bushing fixed with respect to the rotor and mating with the said round bushing in jaw-clutch manner when the rotary means is in the stopped nonblocking position.

9. A device as claimed in claim 6, the bias in said one direction tending to urge at least one of the projections against the receiving means to slow the rotor sufficiently for the projections to enter the slot. 

1. A device for attenuating a radiant energy beam in an analyzer depending on relative radiation absorption by fluids comprising: a rotary means for periodically blocking said beam including a wirelike loop for rotation within said beam about an axis transversely of said beam, the blocking portions of said loop being of substantially less area than the nonblocking portion enclosed by said loop, driving means for rotating said loop about said axis, fixed arresting means positioned about said axis for bringing said rotary means to rest in a nonblocking position relative to said beam, said driving means including means to move said rotating means out of engagement with said arresting means when said driving means are energized and to cause engagement with said arresting means when deenergized.
 2. A device as claimed in claim l, wherein said drive means includes an electric motor having a stator and a rotor movable along the said axis and substantially rigidly connected to said rotary means, the rotor being axially aligned with the rotary means and being biased in one direction along the axis thereof when the stator is not excited and in the opposite direction when the stator becomes excited, said means for bringing the rotary means to rest including fixed receiving means and means fixed with respect to the rotor for entering the receiving means upon movement of the rotor in said one direction to bring the rotary means to a rotary position corresponding to said nonblocking position.
 3. A device as claimed in claim 2, said rotor being biased by gravity in said one direction.
 4. A device as claimed in claim 1, the rotary means being a substantially mono-planar wire loop mounted for rotation about an axis to which the beam is generally perpendicular, the loop lying outside the beam when the loop is in nonblocking position and the axis lying substantially in the plane of the loop.
 5. A device as claimed in claim 4, the loop being substantially symmetrical about said axis.
 6. A device as claimed in claim 2 said receiving means being provided with a slot radial to the axis, and the means for bringing the rotary means to rest also include projections on the rotary means radial from the axis of the axis of the rotary means and developed in said one direction for entry into said receiving means the bias in said one direction urging at least one of the projections against the receiving means to slow the rotor sufficiently for the projections to enter the slot.
 7. A device as claimed in claim 6, the receiving means being a plate to which said axis is perpendicular and having a radial slot, said rotary means including a substantially flat wire loop embracing the beam when in said nonblocking position, the loop having terminal portions forming said radial projections for entering the slot.
 8. A device as claimed in claim 6, said receiving means being a round bushing containing a V-shaped notch thereacross open toward the rotor to provide said slot and a similar slot as a continuation thereof across the axis, and a similar bushing fixed with respect to the rotor and mating with the said round bushing in jaw-clutch manner when the rotary means is in the stopped nonblocking position.
 9. A device as claimed in claim 6, the bias in said one direction tending to urge at least one of the projections against the receiving means to slow the rotor sufficiently for the projections to enter the slot. 